Liquid chromatography is a process used increasingly in analytical and preparative chemistry, whereby a stationary porous material is held in a chamber, such as a long column, while a mobile liquid material is passed through the porous material. In a typical case, the stationary material is an inert powder coated with a stationary liquid agent. Various distinct chemical compounds contained in a carrier liquid (which usually forms the bulk of the mobile liquid) have varying affinities for the stationary liquid agent. Consequently, as the mobile liquid moves through a chromatographic column, various chemical compounds are, as a consequence of their different affinities delayed varying times by their contact with the stationary liquid agent. These various chemicals emerge from the column at different times and are detected individually by a refractometer, an ultra violet light, absorbtometer or some other such analytical apparatus in which the liquid flows on leaving the chromatographic column.
Over the years a good deal of inventive effort has been devoted to the development of equipment for use in liquid chromatography. Much of this effort has been devoted to the design of equipment which would tend to idealize the distribution and flow of the mobile phase through the porous stationary phase. See, for example, U.S. Pat. Nos. 3,522,172, 3,374,606, 3,250,058 and 3,796,657 all of which relate to flow-distribution means placed within the column. Some of the work has been primarily directed to the design of end fittings to optimize the initial distribution of the mobile liquid at the top of the column. See, for example, U.S. Pat. No. 3,334,514 to Catravas and U.S. Pat. No. 3,511,377 to Hrdina wherein conical entrances are disclosed. Other work has related specifically to avoiding preferential flow of liquid between the walls of a column and the packing therein; e.g. see U.S. Pat. No. 3,808,125 to Good.
Problems associated with the design and use of end fittings are particularly difficult when high pressure chromatography is used. Pressures in the range of 1000-6000 psig are frequently used in liquid chromatography. Consequently, very dependable sealing techniques must be used and it is a problem to assure adequate sealing without excessive wear of deformed metal parts. For example, some fittings have ferrules which are tightened about the columns. After use, the shape of the column is materially distorted by the force exerted on the ferrule during tightening of end fittings.
One of the more successful approaches to closing a high-pressure column is the use of a compression screw and ferrule assembly as sold by Waters Associates, Inc. of Milford, Massachusetts. In such a device, the liquid seal between a liquid inlet pipe and the column is achieved by forcing the inlet pipe downwardly with compression screw to form a metal-to-metal seal with the fitting member. The seal is adequate, but there is a necessity of replacing, from time-to-time, the metal-sealing parts.
Applicants, as a consequence of the various problems associated with the end fittings used on chromatographic columns have undertaken to provide a column with superior fittings as is disclosed hereinbelow.